"It's full-speed on to the White House," Clinton told supporters at Indianapolis victory rally. The late-night nail-biter focused on results from Chicago suburb Lake County, where several precincts went strongly for Obama.

Clinton took 53 percent of the vote in suburban areas, compared to 47 percent for Obama, according to CNN exit polls. Clinton also took 68 percent of the rural vote compared to Obama's 32 percent, the exit polls said. Turnout was high, according to Indiana's secretary of state's office.

Eighty-nine percent of Indiana voters said they’d been affected by what they called a recession. When voters were asked who's most likely to improve the economy, 49 percent chose Clinton, 47 percent Obama, said exit polls.

1964: Pro-segregationalist and former Alabama Gov. George Wallace made news in Indiana's Democratic primary by winning nearly one-third of the vote -- 29.8 percent -- a number which surprised some observers of the northern state. According to The New York Times, Wallace's support in Indiana, and in the Wisconsin primary, illustrated the "extent of fears" among whites about the race issue.

1968: Indiana's primary was the first test for the presidential campaign of New York Sen. Robert Kennedy, who had entered the race late. Winning 42 percent of the vote, Kennedy defeated Minnesota Sen. Eugene McCarthy and Indiana's governor. Kennedy also made news during his Indiana campaign when he appealed for calm at a rally hours after the assassination of the Rev. Martin Luther King Jr.

1984: Primary battles between former Vice President Walter Mondale and Colorado Sen. Gary Hart took a twist in Indiana and neighboring Ohio. Hart's narrow victories in the two major industrial states kept his flagging campaign alive and delayed Mondale's eventual clinch of the nomination. A sex scandal eventually forced Hart to drop out of the race.

REPUBLICANS

2000: Texas Gov. George W. Bush was pummeling Arizona Sen. John McCain in their battle for the GOP nomination. Voters in May 2 primaries overwhelmingly cast ballots for Bush in three states -- including Indiana -- where he won with 81 percent. A week later, McCain virtually dropped out of the race by endorsing Bush.

Indiana doesn't register voters by party, so any registered voter may cast ballots in either the GOP or Democratic primary. Voters may be asked to sign a document declaring their affiliation with the party in whose primary they intend to vote. Most convention delegates are allocated proportionally by election results within each congressional district and a lesser number of delegates are allocated based on statewide results.